The potential ability of microwave heating (MWH) for the remediation of marine sediments affected by severe hydrocarbon (HC) contamination was investigated. Decontamination effectiveness and ...environmental sustainability through a comparative Life Cycle Assessment (LCA) were addressed. Main results revealed that the application of a 650-W MWH treatment resulted in a rapid (15min) HC removal. A citric acid (CA) dose of 0.1M led to enhanced-HC removals of 76.9, 96.5 and 99.7% after 5, 10 and 15min of MW irradiation, respectively. The increase in CA dose to 0.2M resulted in a shorter successful remediation time of 10min. The exponential kinetic model adopted showed a good correlation with the experimental data with R2 values in the 0.913–0.987 range. The nature of the MW treatment was shown to differently influence the HC fraction concentration after the irradiation process. Achieved HC removals in such a short remediation time are hardly possible by other clean-up techniques, making the studied treatment a potential excellent choice. Removal mechanisms, which allowed the enhanced-MWH to operate as a highly effective multi-step technique (pure thermal desorption+chemical washing), undoubtedly represent a key factor in the whole remediation process. The LCA highlighted that the MW technology is the most environmentally sustainable alternative for sediment decontamination applications, with a total damage, which was 75.74% lower than that associated with the EK (0.0503pt).
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•A citric acid enhanced-MW treatment of TPH-contaminated sediment was investigated.•The environmental sustainability of the treatment through a LCA study was assessed.•Citric acid/MW resulted in a very rapid and effective (>99%) decontamination.•Results revealed pure thermal desorption and chemical washing as removal mechanisms.•The LCA classified MW technology as the most effective sustainable alternative.
•We investigate a glycerol enhanced-MW treatment of TPH-contaminated sediments.•Results revealed a strong passive ability of sediment in converting MW into heat.•Glycerol addition led to a strong ...increase in sediment MW absorbing ability.•Glycerol/MW resulted in an ultra-rapid (3min) and effective (>99%) decontamination.•No toxic by-products were generated during the remediation treatment.
In this study, a new enhanced MW heating treatment using glycerol was proposed and investigated in the remediation of marine sediments highly contaminated with hydrocarbons. The heating and contaminant removal performance of different treatments using varying glycerol doses were compared. The results showed that the addition of glycerol in sediments largely promoted the MW absorbing performance that corresponded to a large increase in temperature (up to∼120°C) with a maximum sediment temperature of 342°C. This allowed much faster contaminant removal kinetic to be obtained. A glycerol dose of 5% led to drastically lowered contaminant residual concentrations of 6454 (R=∼81%), 770 (R=∼98%) and 12 (R>99%) mgkg−1 after 3, 5 and 10min, respectively, demonstrating that∼5min were sufficient to reach the regulatory remediation target. A further dose increase (10%) led to a required time of 3min (R>99%), which corresponded to almost half of the MW energy required respect to the unenhanced MW. The main advantage of MW/glycerol treatment is the possibility to obtain a very rapid and effective decontamination process potentially reducing energy costs, also in the case of a very high initial hydrocarbon concentration, without producing additional by-products (respect to MW alone), which in some cases can be toxic. A comparison with other available clean-up alternatives revealed that literature does not report similar rapid and at the same time effective treatments for hydrocarbon-contaminated sediments.
